The present invention relates, generally, to a method for controlling combustion in a multi-cylinder engine, and a multi-cylinder engine, and, more particularly, a method for controlling combustion by controlling one or more fuel injection parameters and an engine in which combustion is controlled by controlling one or more fuel injection parameters.
Continued reductions in engine and system-out NOx emissions for heavy duty diesel engines have led to increasing use of exhaust gas recirculation. Upon analyzing cylinder to cylinder charge mass concentrations in certain engines it has been discovered that non-homogeneous EGR and fresh air mixing often occurs. This unbalanced mixing may be harmful to engine components and detrimental to engine performance and emissions.
If EGR concentrations are very high in certain cylinders due to improper mixing, increasing particulate matter (e.g., smoke) and hydrocarbons will be generated during combustion in the EGR-rich cylinder. High amounts of improperly burned carbon may damage a variety of engine components. If the gas is re-circulated from these cylinders into an EGR circuit, the EGR components including but not limited to valves and coolers will be exposed to damaging and fouling effects of such a mixture. Alternatively, if this gas with high levels of particulate matter and hydrocarbons is directed to an after-treatment system, it may over-load or damage the components. Cylinders that are low in EGR concentration will result in higher NOx concentrations and higher combustions temperatures. If the gas output of such a cylinder is directed to the tailpipe and not the EGR circuit, the measured tailpipe emissions may be higher than the actual average of cylinder out emissions.
Most solutions to the problem of unbalanced mixing involve experimentation supported with fluid dynamic modeling to optimize mixing chamber and manifold geometry to achieve more uniform mixing. However, a variety of factors such as component cost and packaging issues may result in a final hardware package that is not optimal for engine performance and emissions. Also, even engines with air handling system that are optimized for particular conditions are typically operated over a broad speed and load range. Flow dynamics may change outside of the designed-for conditions such that the design may be detrimental in mixing in other operating conditions. Some methods exist for reducing cylinder to cylinder power output variance by trimming fueling angles, but no known methods exist for addressing the aforementioned combustion and emissions concerns.
It is desirable to provide a multi-cylinder engine that achieves desired emissions compositions from all cylinders. It is also desirable to provide a method for achieving desired emissions compositions from all cylinders of a multi-cylinder engine.
According to an aspect of the present invention, a method for controlling combustion in a multi-cylinder engine comprises injecting fuel into at least one cylinder of the multi-cylinder engine and, for each cylinder, separately controlling at least one fuel injection parameter to produce a desired exhaust composition for that cylinder.
According to another aspect of the present invention, a multi-cylinder engine comprises a plurality of cylinders, a fuel injector associated with each cylinder of the plurality of cylinders, and a controller arranged to separately control at least one fuel injection parameter for each cylinder to produce a desired exhaust composition for that cylinder.